My working theory is that consumer ideas are both art and engineering. The art component either takes in the mind of the consumer or it doesn't. Like movies or music, sort of. Lots of great engineering teams can't get the art to work with high probability, and even the great consumer internet artists swing and miss as often as they hit (eg odeo vs twitter). And if the art doesn't take, the engineering won't save you.

Whereas the enterprise ideas are mostly engineering - or rather the art lies in really understanding the customer and the domain, which is relatively straightforward for the great enterprise entrepreneurs, because they are already so deep in it and you can easily go talk to the customers one at a time and learn what you need to know to predict success or failure with pretty high confidence. Not easier but different.

These are all gross over generalizations of course. I think of this as a framework for thinking - one of many - not a literal description of the truth in all cases. One lens.